Probing structural homologies in cell-specific glycoproteins in the leech CNS

Three monoclonal antibodies (mAbs) raised against the leech CNS recognize surface antigens on small sets and subsets of neurons or on glial cells. On immunoblots, they all recognize proteins of 130 kDa molecular weight. In addition, they each bind up to several different lower molecular weight forms. The 130 kDa polypeptides recognized by these mAbs are not major proteins on Coomassie blue-stained gels. They behave as glycoproteins on lentil lectin columns but are not major Concanavalin A-binding molecules. These molecules therefore represent a group of lower abundance, cell-type-specific antigens. Structural relationships between these antigens were explored using immunoprecipitation. The glial cell antigen was immunopurified, however, a fraction of the neuronal antigens co-precipitate. The co-precipitation of neuronal antigens raises the possibility that different neuronal antigenic determinants are carried on the same protein molecule. Such a protein may be modified to carry either one or both neuronal determinants, and could serve as a tag to physiologically delineate subsets of neurons nested within larger neuronal sets.